1. Field of the Invention
The present invention relates to a fixing apparatus including a toner releasing agent applying device, and an image forming apparatus including the same fixing apparatus.
2. Discussion of the Background
An electrophotographic image forming apparatus includes a fixing apparatus for fixing a toner image on a recording material. Generally, the fixing apparatus includes a roller or belt-like shaped fixing member arranged extending in a width direction of a recording material, and a roller or belt-like shaped pressing member which press-contacts and rotates with the fixing member. At least one of the fixing member and the pressing member is heated to a predetermined temperature or greater. A toner image on a recording material is fused and fixed thereon under the influence of heat and pressure while the recording material passes through a nip part between the fixing member and the pressing member. Especially in a fixing apparatus for use in an image forming apparatus that forms a color image with multicolor toner, at least one of the fixing member and the pressing member is kept at a high temperature for enhancing toner fixing performance.
The surfaces of the fixing member and the pressing member are coated with a low frictional material such as silicone rubber in order to prevent fused toner from adhering to the surfaces of the fixing member and the pressing member. Further, toner releasing agent such as silicone oil (hereinafter simply referred to as oil) is uniformly applied onto the coated surfaces of the fixing member and the pressing member by a toner releasing agent applying device (hereinafter simply referred to as oil applying device).
The oil applying device includes an oil applying member such as a roller which is arranged extending in a longitudinal direction of the fixing member, and which uniformly applies oil onto the fixing member. The oil applying device further including an oil pan arranged below the oil applying member to hold oil therein, and an oil delivering member which delivers the oil in the oil pan to the oil applying member.
In order to uniformly supply oil to the oil applying member, the oil delivering member includes a band shaped felt member extending in a width direction of a recording material. The oil delivering member is attached to a bracket arranged in a vicinity of the oil applying member, and one or two extending parts, which extend to the oil pan, are provided with the oil delivering member. Thus, the oil delivering member is arranged to function as a bridge between the oil pan and the oil applying member. With this configuration, oil in the oil pan is taken up by capillary phenomenon of the extending part, so that the oil delivering member is soaked with the oil.
As an alternative to a method of taking up oil in the oil pan by use of capillary phenomenon, another method in which oil is dropped to a substantially center part of an oil supply member by an oil conveying device may be employed.
In the above-described fixing apparatus including the oil applying device, it takes time to supply oil to the oil applying member. This is because oil is supplied from the oil pan arranged below the oil applying member to the oil applying member all by use of capillary phenomenon of a felt member as the oil delivering member. Therefore, when toner images are consecutively formed on recording materials, and the recording materials having unfixed toner images are consecutively conveyed to the fixing apparatus, oil cannot be supplied to the oil applying member in time, so that sufficient oil cannot be uniformly applied onto the fixing member. In the worst case, the fixing member may lack oil. When the fixing member runs out of oil, a so called offset condition tends to occur, in which fused toner adheres to the fixing member and the toner adhered to the fixing member re-transfers onto a recording material.
Further, as compared to a case in which the fixing member is applied with sufficient oil, abrasion of the fixing member and the pressing member due to contact with a recording material is increased, thereby hastening deterioration of the fixing member and the pressing member. Such defect is likely to occur especially in a color image forming apparatus in which a color toner image is fixed at a relatively high temperature.
In a fixing apparatus employing the above-described another method in which oil is dropped to a substantially center part of the oil supply member by the oil conveying device, the oil supply member tends to lack the oil around end portions thereof. This is because the oil is supplied to the oil supply member at one substantially center part thereof. Although the end portions of the oil supply member can be supplied with sufficient oil by increasing the number of oil supply points, this may cause complexity of the construction of the fixing apparatus.
According to one aspect of the present invention, a fixing apparatus for fixing a toner image on a recording material includes a fixing member arranged on a recording material conveying path, a pressing member configured to press-contact a surface of the fixing member, and a toner releasing agent applying device configured to convey and apply toner releasing agent onto the surface of the fixing member. The toner releasing agent applying device includes a toner releasing agent holding unit configured to hold toner releasing agent and including a toner releasing agent supply opening, a permeable toner releasing agent delivering member configured to deliver toner releasing agent from the toner releasing agent holding unit to the surface of the fixing member, the toner releasing agent delivering member being supplied with the toner releasing agent in the toner releasing agent holding unit through the toner releasing agent supply opening, and a toner releasing agent conveying unit configured to convey toner releasing agent to the toner releasing agent holding unit.
According to another aspect of the present invention, the toner releasing agent holding unit may be arranged in a vicinity of the fixing member and opposite to the fixing member at a distance apart, and the toner releasing agent delivering member may be arranged between the toner releasing agent holding unit and the fixing member, and the toner releasing agent delivering member may include a first end surface which contacts the fixing member, and a second end surface opposing the first end surface and facing an inside of the toner releasing agent holding unit through the toner releasing agent supply opening.
According to another aspect of the present invention, the toner releasing agent applying device may further include at least one toner releasing agent applying member configured to apply toner releasing agent onto the surface of the fixing member, and the toner releasing agent holding unit may be arranged in a vicinity of at least one toner releasing agent applying member and opposite to at least one toner releasing agent applying member at a distance apart, and the toner releasing agent delivering member may be arranged between the toner releasing agent holding unit and at least one toner releasing agent applying member, and the toner releasing agent delivering member may include a first end surface which contacts at least one toner releasing agent applying member, and a second end surface opposing the first end surface and facing an inside of the toner releasing agent holding unit through the toner releasing agent supply opening.
Objects, features, and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.